1. Field of the Invention
The present invention relates to writing data onto a disk of a hard disk drive.
2. Background Information
Hard disk drives contain a plurality of magnetic heads that are coupled to rotating disks. The heads can magnetize and sense the magnetic fields of the disks to write and read data, respectively. The heads are coupled to a pivoting actuator arm that has a voice coil motor.
Data is typically stored on tracks that extend radially across the disk surfaces. The voice coil motor can be energized to pivot the actuator arm and move the heads to different track locations. Each track is typically divided into a number of sectors. Each sector contains at least one data field.
The disk drive typically writes data in blocks across a number of data sectors. Data is written by providing a write current to a coil of each head. The coil generates a magnetic flux that magnetizes the disk. Conversely, data is read through a read element in the head that senses a magnetic field of the disk. The signal sensed by the read element is provided to a pre-amplifier circuit. The signal is digitized and processed into a series of bits.
The read/write signal is processed using a number of read/write channel parameters. By way of example, there may be read channel parameters like cutoff frequency, gain, and boost; and write channel parameters like write current, overshoot duration, and write pre-compensation.
The rate at which data is written may vary for different locations of the disk. For example, the data rate at the outer diameter of the disk may be, twice that of the data rate at the disk inner diameter. Data rate is sometimes characterized by the width between bits also known as “T”. The inner diameter may have a data rate of 2 T, while the outer diameter is written at a rate of T.
The overshoot duration write channel parameter is used to optimize the writing of data. The overshoot duration cannot be wider than T at the lowest data rate. To insure that this does not occur, the overshoot duration range is selected at the lowest data rate. Having an overshoot duration range set at the lowest data rate limits the ability to optimize writing at the higher data rates.